Various cereal products and baked goods are sweetened during preparation either by incorporating a sweetening ingredient in the starting mix prior to baking, or by applying a sweetening composition to the product after it has been baked. In the past, the sweetening agent generally employed for such purposes has been a nutritive carbohydrate sweetener, such as sucrose, fructose, corn syrup and the like. More recently, efforts have been made to replace the aforesaid carbohydrate sweeteners in baked comestibles due to concern over the effect of such sweeteners upon diet and dental health. Among the substitute sweetening agents proposed have been L-aspartic acid sweetening derivatives, particularly the dipeptide N-L-.alpha.-aspartyl-L-phenylalanine methyl ester (aspartame).
The L-aspartic acid sweetening derivatives are potent sweetening agents, reportedly being, gram-for-gram, 100 to 200 times as sweet as sucrose. The intense sweetness produced by these compounds results in negligible calories when used at isosweet levels in place of sucrose. Similarly, the L-aspartic acid derivatives generally possess negligible cariogenicity.
The L-aspartic acid sweetening derivatives are known to be moisture sensitive, in that they contain an ester linkage that may hydrolyze to a dipeptide, which, in turn, may cyclize to the corresponding diketopiperazine (DKP), with a corresponding loss of sweetness. However, relatively stable solutions of these compounds may be prepared under controlled conditions of temperature and pH. An aqueous solution of aspartame, for example, has maximum stability at ambient temperature at a pH of about 4.3. Aspartame exhibits a maximum water solubility, (approximately 10 gm/100 ml at 20.degree. C.) at a pH of 2.2 and a minimum solubility (approximately 1.0 gm/100 ml at 20.degree. C.) at a pH of 5.2, its isoelectric point. Solubility increases with temperature increase.
The L-aspartic acid sweetening derivatives also tend to decompose to DKP at elevated temperature, with attendant loss of sweetness.
As a result of the heat instability problem a number of processes have been proposed in which a coating composition comprising the L-aspartic acid sweetening derivative is applied to the surface of the already baked comestible to reduce exposure of the sweetening derivative to elevated temperature over an extended period. However, because of the moisture sensitivity and relatively low solubility of the L-aspartic acid sweetening derivatives, the use of aqueous solutions thereof as a sweetening composition has been avoided. Incomplete solution of the L-aspartic acid sweetening derivatives tends to result in non-uniform sweetening in topical applications of such sweetening derivatives to the exterior of a baked comestible. Non-uniformity of application of these sweetening derivatives is a concern because of the production of "hot spots", which is an expression used by those experienced in the art to refer to a non-uniform sweetening response attributable to high concentrations of the sweetener at discrete locations on the foodstuff.
Various procedures have been suggested for applying L-aspartic acid derivative-containing sweetening compositions to baked comestibles, so as to overcome the moisture sensitivity and ameliorate the adverse effect produced by low solubility of these sweetening derivatives. Included among the suggested procedures have been several which involve encapsulating or coating particles of the L-aspartic acid derivative with edible coating materials followed by drying and granulation.
In U.S. Pat. No. 3,962,468, particles of L-aspartic acid derivatives are stabilized in a dry fixation by causing a slurry-forming level of undissolved hydrated particles of the sweetening agent to be dispersed in an aqueous dextrin solution as discretely distributed, undissolved particles, and drying the dispersion to encapsulate the particles of the L-aspartic acid derivative in the dextrin.
In U.S. Pat. No. 4,004,039, aspartame crystals are stabilized into a particulate form so as to be freeflowing with other powdered materials. The stabilization process involves admixing the crystals with a matrix-forming material such as dried coffee extract, whey, low dextrose equivalent starch polymers and protein extracts, heating the admixture to form a melt, in which the ester crystals are discretely distributed, calendering the melt between two rollers to submerge the crystals in the melt, cooling the same, and then granulating the products to produce particles which encapsulate the crystals distributed therein.
In U.S. Pat. No. 3,934,048, dipeptide sweeteners, including aspartame, are provided with a satisfactory rate of solubility and storage stability due to low hygroscopicity, by co-drying a solution of the dipeptide and an edible, bland, low-calorie polysaccharide.
Encapsulating or coating L-aspartic acid sweetening derivatives in the above manner, purportedly has the advantage of providing a comestible having the sweetening derivative in a relatively low hygroscopic state that achieves sweetness uniformity.
An approach to coating comestibles such as cereal products, baked goods and confectionary foodstuffs with an L-aspartic acid derivative containing-coating which attempts to minimize the above-noted problems caused by the thermal instability and low solubility of such sweetening derivatives is described in U.S. Pat. No. 3,955,000. In that process, the L-aspartic acid derivatives are admixed in aqueous suspension with a starch hydrolyzate comprising predominantly oligosaccharide solids having a low dextrose equivalency, of about less than 30, and applied as a coating solution to the comestible. The coating of the dried solution, it is disclosed, smoothes out the taste impact generated by any sweetening imbalance attributable to the incomplete solution of the sweetening derivative, or non-uniformity of its dispersion. The uniform distribution of sweetness, and attendant minimizing of "hot spots" when the food is eaten, is attributed principally to the starch hydrolyzate.
The coating solution used in the process of U.S. Pat. No. 3,955,000 is maintained at a temperature below 200.degree. F. so as to have the L-aspartic acid derivative dispersed therein as undissolved hydrated particles. The solution is applied to the foodstuff by atomization or other spray techniques. The coated comestible, it is disclosed, is dried at product temperatures which do not exceed 200.degree. F. in order to assure that the sweetening agent is not degraded. The coated comestible is dried to a stable moisture content of below about 8%.
The coating process of U.S. Pat. No. 3,955,000 produces a frosted or glazed product that has a sugar-coated appearance. Other substances, such as fat and starches, it is disclosed, can be incorporated in the coating to create a dull or crystalline appearance suggestive of other sweetened cereal applications. However, the appearance of a sugar coating, whether glazed or dull, is associated with an undesirable amount of sugar by many consumers. Further, the dextrins, and other additives in the coating, increase the calorific value of the foodstuff.
Still another prior art attempt to prepare comestibles having an L-aspartic acid derivative containing-coating is described in U.S. Pat. No. 4,378,377. The process involves preparing a coating composition comprising the sweetening derivative and hydrolyzed or unhydrolyzed vegetable protein isolates in an aqueous suspension, "enrobing" the comestible with the coating composition in an amount sufficient to provide the desired level of sweetness, and drying the coated comestible to a final moisture content of less than about 5.0%. The aqueous suspension essentially comprises, by weight, from about 0.1% to 4.0% sweetening derivative and from about 1% to about 30% vegetable protein. The weight ratio of aqueous suspension to comestible base may vary depending on the level of sweetness desired in the coating and the concentration of the sweetening derivative in the aqueous suspension. In general, the weight ratio of aqueous suspension of comestible base may range from about 1:12 to about 1:1.3, a weight ratio in the range from about 1:9 to about 1:3 being preferred. The enrobing step is generally practiced at a temperature of from about 50.degree. F. to 100.degree. F. for both the comestible base and the aqueous suspension. Any conventional enrobing technique may be employed, such as tumbling or spraying.
The proteinaceous suspending agents function to maintain the sweetening derivative in suspension, (i.e. a large fraction of the sweetener will not be dissolved, but will be suspended and dispersed), to bind the sweetening derivative to the surface of the comestible, and to aid in the even distribution of the suspension over the comestible base during enrobing. The use of the L-aspartic acid sweetening derivative and the vegetable protein isolates in combination, it is disclosed, has the advantage of permitting the use of ambient temperature or "cold water" aqueous suspensions in preparing coated comestibles, thereby minimizing thermal degradation of the sweetening derivative and attendance loss of sweetness.
The finished sweetened product, it is disclosed, has a sweetness profile similar to sucrose-sweetened comestibles and desirably comprises from about 0.05% to 0.4% of sweetening derivative and from about 1% to 20% of vegetable protein (dry weight). However, comestibles produced according to the process of U.S. Pat. No. 4,378,377 also have the appearance of having a sugar-coating which, as noted above, is associated with an excessive sugar content by many consumers. Moreover, the vegetable protein isolates used to provide the coating, such as soy protein isolates, often produce a slightly bitter aftertaste.
The process for sweetening baked comestibles according to the present invention provides an acceptable level of sweetness in the final products without providing a sugar coated appearance. The process enables the sweetening of natural products, such as shredded wheat, while retaining their natural appearance. The sweetening derivative is uniformily applied to the comestible, so that the occurrence of "hot spots" is at least substantially avoided. In practicing the present invention, it is unnecessary to encapsulate the sweetening derivative or incorporate a carrier or fixative therewith in order to prevent moisture degradation and consequential loss of sweetness. It is believed that the sweetening derivative is absorbed into the body of the foodstuff, and thereby protected from the deleterious effects of moisture, as opposed to remaining on the surface thereof where it may more readily undergo decomposition. Further, because the sweetening process of this invention requires no carrier or fixative, which generally are substances of relatively high viscosity, it is easier to operate than a process involving the application of a coating composition containing such additives. A decided advantage of the process of this invention is that minimal, if any, drying or heating of the sweetened baked comestible is required. Thus, unlike some of the prior art coating processes described above, in which drying at elevated temperature is an essential process step, the present invention involves no risk of thermal degradation of the L-aspartic acid sweetening derivative incorporated in the final product.
The products produced by the process of this invention are comestibles, such as cereal products and baked goods which have an L-aspartic acid sweetening derivative uniformily applied thereto, and exhibit a uniform sweetening response when eaten, but which do not have a sugar-coated appearance. These products also possess excellent shelf-stability.
The present invention is effective for sweetening a variety of comestibles with an L-aspartic acid sweetening derivative while retaining a natural product appearance. It is considerably more economical than the encapsulating, coating, or enrobing processes proposed heretofore.